With an explosive growth of mobile communications, we are facing with a problem of shortage of frequency spectrum and capacity. Moreover there is a growing need for multi-media communications including picture and video transmission. It is therefore strongly desired to construct an accurate channel modeling in order to establish the high-speed digital mobile communication systems, and also to make a measuring system for channel characteristics at microwave frequency band.In this study, we constructed the measurement systems for channel characteristics in both space and time domain from the view point of high-speed digital mobile communications. At first we made an off-Line measurement system, and then tried to make an on-line system based on DSP's. Specifically, we succeeded to develop a multi-dimensional estimation scheme capable to estimate DOA, DOT and Signal Power level simultaneously under the condition of limited number of array antennas and measuring frequency. We developed a novel type co estimation algorithm by means of neural network and convex programming technique.Furthermore we proposed several types of adaptive signal processing systems by using the above mentioned results. Main achievements are the array signal processing by using a multi-carrier transmission scheme, the relationship of diversity technique and beam forming technique, the novel precoding techniques utilizing DOA and DOT information and the multi-dimensional ESPRIT.Combined array signal processing are a promising technique for the improvement of transmission quality i.e. fast tracking and packet through rate.